FGD gypsum dehydration difficulties of LYWSQ the seed crystal coagulant Abstract: of gypsum dehydration of limestone / gypsum wet flue gas desulfurization running difficult reasons, find solutions to problems through the practical experience of testing and operation targeted the desulfurization run The gypsum slurry is improved, significantly improve the dehydration effect. Keywords: desulfurization; gypsum; dehydration difficult; solution, technical background thermal power generating units desulfurization wet FGD technology limestone - gypsum wet desulfurization process, which is characterized by the absorber using single-loop spray tower, desulfurization device uses a furnace a tower; flue gas system is not using the flue gas heat exchanger (GGH); limestone pulping system using limestone by a wet ball mill grinding filtrate was diluted pulp; desulfurization by-product - gypsum dewatering moisture content of less than 10%, The gypsum content of greater than 90% (dry basis). Desulfurization efficiency not less than 95%, 95% of the utilization of the desulfurization apparatus, each of the vacuum belt dehydrating machine processing capacity of 25t / h. Second, the process in this process, the limestone slurry within the flue gas in the absorber countercurrent washing, forming a half of water that calcium sulfite and transferred to the slurry in small particulate air forced oxidation of the calcium sulfate dihydrate (CaSO4 · 2H2O) crystals. Plaster discharge pump out of the absorber slurry, sent to the gypsum cyclone, concentration and particle size fractionation, dilute slurry overflow to the filtrate tank; concentrated underflow slurry is sent to the vacuum belt conveyor dehydration of gypsum. Dehydrated gypsum moisture content is generally controlled at 10% (mass content) The following standards. If the gypsum water is too high, not only affect the normal operation of the desulfurization systems and equipment, and gypsum storage, transportation and post-processing can cause some difficulties (such as pictures), therefore, should control. Photo 1: gypsum moisture content, the transportation is very difficult, there is a problem desulphurization system in operation due to the dramatic changes in other parameters, appears more than once the high moisture content of gypsum, causing the vacuum belt unit fails to work effectively. This phenomenon is a long time can not be improved, and in severe desulfurization unit forced outage, a direct impact on the desulfurization investment rate. This appears the most direct way is measured by the professional laboratory analysis to come to the root of the problem, but the laboratory has not been established, so that to solve the problem only with the practical experience of running, the following desulfurization run the cause of the problem of the high moisture content of gypsum and simple solution to carry out exchanges. Fourth, analysis of causes desulfurization run the gypsum water content, the performance of gypsum offline feed opening non-caking, do not fall into a mud-like, or even lower viscous into the upper water-like. This dehydration of the material and the physical properties of a viscous, analyze the causes are generally the following situations: 1, entry high dust content, lead absorber slurry poisoning ", limestone quality change, coal sulfur content of a sudden 4 larger, gypsum swirler abnormal 5, abnormal vacuum belt conveyor 6, the amount of oxidation air is less than seven, five other reasons, the WebSite high dust content of the original flue gas fly ash enters the absorber slurry in some extent hindered the SO2 and desulfurization agent of contact, reducing the dissolution rate of limestone in Ca2 +'s, at the same time some of the heavy metals in fly ash constantly dissolution such as Hg, Mg, Cd, Zn and other ions will inhibit the Ca2 + and HSO3-reaction, "closed" the absorbent activity. General requirements absorber inlet dust content can not exceed 200mg/m3, if more than 200 mg/m3 more prone to this phenomenon. If you the soot content measuring instruments are not allowed, the most direct way sampling precipitation, precipitation of solids in the upper part of the black ash-like substance more than 1/3 of the total (normal should be less than 1/4), it shows the entrance The smoke and dust content is too large (such as pictures). Picture 2: Left slurry containing a large quantity of ash precipitation sampling photos right side of the normal slurry sampling precipitation photos VI, the absorber slurry "poisoning" due to the electrostatic precipitator efficiency is not very good, the absorber into a vacuum cleaner, The absorber slurry blackened, blistering, dehydration of gypsum layer of black material (such as pictures), to stay alive in this situation can be imagined. The absorber slurry can easily "poisoned". Event of the phenomenon of "poisoning" the slurry discharge all replacement fresh slurry, resulting in a great waste, and affect the normal input of the desulfurization system. The absorber slurry "poisoning", a half months to correct to a radical improvement in the meantime, will waste a lot of limestone, emit large quantities of slurry, and increased operating costs. Image 3: containing a large quantity of ash, the status when the belt dehydrating VII, limestone quality change limestone quality is an important factor affecting the desulfurization run, wherein the calcium carbonate content and the fineness of the finished product is the key to the impurities increased or decreased will so that the the slurry quality deterioration, the finer the fineness of the reaction, the better. This may be changed greatly when the carbonate content and the fineness of the finished product, reduce its reactivity highly likely to occur for the excess slurry, then tower slurry containing CaCO3 volume increases, easily bonded by the limestone particles in together, resulting in the difficulty caused by dehydration phenomena occur. Limestone clay, sand and other impurities entrained, unstable state of these impurities will be caused to some extent difficult dehydration occurs. , Coal sulfur content increases suddenly when the absorber inlet SO2 concentration larger, and not increase the amount of air blown into the absorber oxidation the oxidation air volume can not be changed, especially when the SO2 concentration exceeds the design value, due to the lack of severe oxidation, will cause difficulties in crystallization of gypsum, increase the difficulty of dehydration. 9, gypsum cyclone abnormal determine the cyclone is working properly, you can take the examination and measurement methods. Measurement method is very simple, were taken into gypsum cyclone imports, exports slurry, settling for 30 minutes, the to compare solids content difference, if the inlet solids content of 40-60% of the export Description the swirl child is running properly , if more than 60% is necessary to check and replace the cyclone sub. One can imagine that if the gypsum slurry into the vacuum belt conveyor is too thin, vacuum precipitation excessive water. Can not form a vacuum dewatering process, so that the dehydrating effect is also deteriorated. Ten, the abnormal vacuum vacuum belt conveyor belt machine is secondary gypsum dehydration equipment, the nature of the effects of dehydration and slurry, the cleanliness of the cloth have a greater relationship. Vapor-liquid separator meter directly reflects the vacuum, vacuum belt conveyor belt conveyor vacuum plaster moisture content was regularly change the belt conveyor vacuum increased, reflecting the treatment by the increase in the pressure drop of the filter cloth, reflect the increased moisture content of gypsum. The increase is due to the dewatering equipment is not operating properly, such as filter cloth washing dirty or the cloth life cycle is too long will the belt conveyor deterioration of the effects of dehydration, dehydration, poor; Second, the changing nature of the gypsum slurry, such as slurry The increase in small and medium-sized particles of gypsum crystals or the impurity content of the slurry is caused by the increase in channel clogging of the filter cloth, so that the water in the slurry is not easily separated from the cloth pores. To achieve the effect of solid-liquid separation, must the vacuum pressure. 11, the amount of oxidation air when coal-fired sulfur increases, prone to the phenomenon of incomplete oxidation. When the oxidation rate is decreased, the soluble sulphite concentration in the slurry increases, the fiction of the dissolution of CaCO3, the purity of the gypsum will also drop, wherein the CaCO3 increases, the smaller the particle size of the CaCO3 easily adsorbed to a vacuum belt dryer filter cloth, resulting in dehydration problems. When the sample from the absorber can be found in the slurry into an off-white precipitate was slower, normal gypsum slurry more 20-minute settling time, the need for about 1 hour. 12, for other reasons in addition to the above reasons, there are operating parameter control. Slurry density is too low, the the instrument distortion caused by error in judgment, PH value control unstable absorber within the CL-content is too high and other reasons. 13, corresponding way to solve the problem absorber gypsum slurry dehydration abnormal situation, how to improve the dehydration effect as soon as possible, to ensure that qualified gypsum quality is the key to running. Consult the relevant authority of the experts, most of them are all replacement slurry, but the impact of this approach for a long time to reach the immediate effect. Often desulfurization system and not long-term outage, combined desulfurization check more impossible for a long time to correct. Through exploring the Luoyang high mountains Application Engineering Co., Ltd. found a simple way to solve the problem in the actual operation, only need to add a high-tech gypsum dehydration difficult seed crystal coagulant in the desulfurization tower, plus state-of-the-art gypsum dewatering difficult adjustment technique, even in the case of stop chasing, i.e. able to solve the difficult problem of dehydration of gypsum. 14, the application effect of this method after a number of power plant gypsum dehydration verification, the gypsum dewatering difficult in recent years, are solved in a very short time. Think about the principle: that is, for whatever reason the balance of the tower destroyed replenished FGD gypsum dehydration difficult seed crystal the coagulant to restore the original environment, to establish the balance of the tower, the problem will be solved. The principle of specific chemical analysis is no longer described, welcomed the consultation and cooperation.